Amplifier tube



July 31, 1934- P. R. DYKSTERHUIS y 1,958,248

AMPLIFIER TUBE Filed Aug. 30, 1930 POPKO RHNDER DYKSTERHUIS ATTORN EY fateritecl Jnul-y 31, 1934 PATENT OFFICE AMPLIFIER TUBE y Pepke Reinder Dyksterhuis, Eindhoven, Netherlands, assigner to Radio Corporation of Amer- I ica, a'corporation of Delaware 1 Application August 30, 1930, Serial No. 478,833

. In the Netherlands September 30, 1929 '8 Claims. (CL 179-171) The present invention relates to amplifiers, and more particularly to improvements in, or relating to, circuit arrangements for amplifying tubes with `so-,called parallel feeding.

The so-called parallel feeding of amplifying valves has the advantage that the core of the amplifier transformers is free of direct vcurrent magnetization, owing to which one of the most important'causes of distortion is suppressed, and the transformer may be given much smaller dimensions. However, with the usual circuit arrangements these advantagesare obtained at the cost of the amplification and economy, for in order to keep the same amplification and to leave ,unaltered the linear course of the characteristic Ycurve of the coupling transformer, choke-coil or auto-transformer, it would benecessaryto supply the anode current through an infinitely high alternating vcurrent resistance, while the alternating current must be supplied to the coupling element through a condenserof infinitely high capacity. f

, As a rule, a compromise is made and forthe sake of economy,l a portion of the attainable amplification isv given up. One is notwithstanding compelledto employ choke-coils having a selfv inductance which isl afew times as large as that ofthe primary winding of the coupling transformer, while, in addition, the -.value of the capacity connected in series is very high, said value being as a rule of the order of magnitude of two microfarads. 1

yThe present invention has for 'its main object to provide means permitting better-results with ,considerably smaller values of inductance` and capacity of the said elements. This affords the vdouble advantage of the-working being improved and the .manufacture being made cheaper.

Thesey advantages are obtained by. judiciously -dimensioning the parallel inductance and the series capacity. Thus, according to the invention, the self-induction of the choke-coil is chosen so as to be from 1 to 2vtimes as large as .theY selfinduction` of the'primary winding of the.v cou- "pling transformer, and besides, .the damping of the circuitformed by the internal resistance of the valve, the series .condenser andthe primary winding of the transformer, is made equal tothe angular' frequency vof the natural oscillation `of the circuit constituted by the primaryA winding, and theseries-condenser while neglectingthe loss resistance. It is evident that it does not .matter which ofthe various elements should be considered to be given provided that the said relation is satisfied. The frequency'of the said natural oscillation should conveniently be so chosen as to be substantially equal to 50 to 100. From this point on, the frequency characteristic curve has a substantially fiat course and not until the region of the high tones does the curve de- Viate, and does it fall more or less abruptly according to circumstances.

In the high regions 'of the audible frequencies the characteristic curve can be straightened by connecting an inductance coil between the series condenser and the primary winding of the transformer, and by connecting a condenser in parallel to the said winding, the self-inductance and .the capacity of these elements being so chosen that the 'natural frequency of the circuit consti- 70 tuted by these elements is'located in the high portion of the sound spectrum while the damping of the circuit formed by these elements in series with the internal resistance of the corresponding valve, (consequently, practically the internal revsistance of the valve divided by the impedance of the inductance at the said frequency) is smaller than unity.

At this choice of the various magnitudes an amplification characteristic curve is obtained ywhichfromb() to 100 cycles up to 9 to 10,000

cycles is substantially straight, and abruptly falls downwards both on the 10W and on the high Side.

Ifan additional condenser is connected in parallel to the anode-filament circuit of the valve,

Vthe characteristic curvewill fall on the high side still more abruptly, and, besides, feed back effects, which at the high frequencies may be troublesome, will be suppressed.

The novel features which I believe to be charvacteristic of my invention are set forth in pardicated diagrammatically several circuit organizations whereby my invention may be carried into effect. n

In Fig. 1, R1 is a triode, Le a choke coil, C1 a 100 condenser, L1 the primary vwinding of a transformer whose secondary winding L2 is included in the grid circuit of the next triode conventionally shown as a utilization means, Le is connected on one side to the anode of the valve 1, and on the other side to the positive terminal of a source of anode current, the source not being shown. C1

and L1 are connected in series between the anode and the cathode of the Valvejl, the internal resistance of this valve beingassumed to be R1.

El: 1 L1 i/Llc1 At a given value of R1 and consequently with a value it is possible to obtain any desired (2) =VV1 (The angular frequency)v value cf W1 by a suitable choice of the valueiof L1. For the reproduction of speech and rnusic it is usually suihcient to take W1 equal 'to about 1660 (pitch of tone v v and at any rate it is notfnecessary toitakelwW1 smaller than 300.

The dimensioning indicated renderssit possible to take the ratio of transformation 'ofthe coupiing transformer considerably,glargenthanfwith the 'transformers hitherto-.known Whereas. np to the present, one wasfebliged-tQ-aeStrict--Qneselr" to a ratio of 1:3,.the invention allows, without any objection, to go a? liighfas lizlOiwith-the usual triodes havinganinternal resista-nce of the order of magnitude of lihf-,ohrns `}Ihe1abo ve described circuit arrangement-verve@particularly favorable results in the:lcwfportionmgthe frequency range to be transmitted.

For transmitting, ,in` aciditipn;y the ahighvpontion with substantially thefsamegstrength use -may be made or" the circuit arrangementsshewnfin -rig. 2 in which between Vthe seriesv condenser and .inarywinding is connected a lter element L3 C3, tc which maybe addedpif'ldesi-red, acondenserjC4.

Fig. 3 :represents the.; substitution` diagram ,of the circuit `arrangement according'tdilig.' 2. It appearsifrom Fig.` l'thatthelwhole. of'it maybe taken as a system of two .coupled circuits, namely:

(l-c- L1 is the leakage inductance offthetransformer, and R21 andCzlfrepresent the secondary resistance and thezselfecapacity plus `the. load capacity of 4.the transformer transformed yto ythe primary side. i. Liis the primary.inductance,'the

`impedance vof which maywbe considered inthis case as being practically innite. TheL resonance .(leakage resonance) of the.circuit.(1-.lc2) L1, C21 is 'practically locatedat ab0ut;5000 cycles. L3 `and Cs are so chosen that is 'or the orderof magnitude '0,540,000 (about 7000 cycles).

Furthermore, L3 is so `'chosen that:

R1=104 ohms ALs: 12 I-I L1=10 E f 01:0.1/1 F LZ1-1000 H 1-k2=0.015

`to L100.

descent at the high frequencies is still more iabrupt.

'The curves A and B represent the frequency characteristics obtained if C3=C4=L3=0 (curve A), and for the value C3=0 (curve B), the other values remaining unaltered.

While I `have indicated and described several systems for carrying my invention into effect, it

f-willbeapparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications may be made without departing the appended claims.

Aprimary circuit connected ato: dsaid,anodecircuit lthrough said condenser, the.fself-inductance-iof the inductance having a :val-ue from-onesto two i195 times as large as `the self-ind-uctance ofther--said .-prirnarycircuit, and thefratio'of the internal rimpedance of 'the tube to `the-rselfeinductance'fof fthe primary circuit Abeing substantielly-iequalY to Ethe value of the natural angular frequency of-thepath W0 including `the said'condenser and primary-circuit.

2.V In an amplier, the combination-off--anelectron'discharge' tube --provided with an a'mde v`oircuit,-van inductance-connecteddn 'said -circuit; J a condenser, andi a transformer --provided-with' a"H5 primary circuitY connected to-sajid anode-'- circuit through said condenser, the self-inductancebf the indue-tance -ha'vinga-yaluefromsoneto two `times-as large as 'the iself-inductanceof theisaid primaryci-rcuit; and-the ratioeof i' the interna'lci-m-f '5520 pedance'o the ltube to ithe self-inductance of--the primary ,circuit being substantially equal 'to lthe Avalue offthe'natural' angular" frequency nfy the pathA including the --said condenser and primary circuitrsaidi natural frequency 4being-between*50"25 3. In an amplifier, the combination-ofanielectron discharge tube provided-witlrananode 3:cir- -cuit,' an inducta-nce connected in-said-circuit; a condenser; and a transformerprovidediwithfaBO primary circuit connected to said? anode 'circuit `throughsaid condenser, 4the s'elf-inductancebf the inductance having avalue'fromone to'itwo times as largeas the se'lfeindu'ctanceI of'rthe-said 'primary circuit, and the'ratio Nof 'the Uinternal 135 impedance of `the tube tok the self -inductanceof ltheprimaryicircuit being substantially equal-*to "the value of lthe;natural'angularffrequency 'of the j pathin'cluding'the said Y :condenser Aandi` primary 'circuit, and a loadv circuit connected in fthe-sec- 1'40 ondary circuit of -said transformen `Ll. In anV ainplier, the 'combinationof anelectron discharge-tube provided' with an-anode-cir cuit; an; inductanceconnected-gin said" circuit;` a

condenser, and a transformer provided1withati45 primary circuitl Vconnected to said anode Acircuit through said-condenser, the Vself--inductanceof @the linductance having a lvalue -frorn-one fto two times as largeas fthev self-inductance offfthe said `primary circuit, and the ratio f of the` internal 5550 impedance of the tube to the self-inductance of the primary circuit being substantially equal to the value of the natural angular frequency of the path including the said condenser and primary circuit, an inductance coil between the condenser and primary circuit, and a condenser connected in parallel with the latter, the coil and parallel condenser being so chosen as to be resonant to a frequency at the high frequency end of the amplifier frequency range.

5. In an amplifier, the combination of an electron discharge tube provided with an anode circuit, an inductance connected in said circuit, a condenser, and a transformer provided with a primary circuit connected to said anode circuit through said condenser, the self-inductance of the inductance having a value from one to two times as large as the self-inductance of the said primary circuit, and the ratio of the internal impedance of the tube to the self-inductance of the primary circuit being substantially equal to the value of the natural angular frequency of the path including the said condenser and primary circuit, a network, resonant to a frequency at the high frequency end of the amplifier frequency range, between the condenser and primary circuit, and an additional condenser connected in parallel with the anode and cathode of said tube.

6. In an amplifier, the combination with a tube provided with an anode circuit, a choke coil connected in the circuit, a source of anode potential connected to the coil, -a capacity, an inductive coupling means connected to said anode circuit through said capacity, said coupling means being resonant to a frequency at the low frequency end of the amplifier frequency range, and a network connected between the capacity and coupling means, the network being resonant to a frequency at the high frequency end of the amplifier frequency range.

7. In an amplifier, the combination with a tube provided with an anode circuit, an inductance coil connected in the circuit, a capacity, an inductive coupling means connected to said anode circuit through said capacity, said coupling means being resonant to a frequency atthe low frequency end of the amplifier frequency range, and a network connected between the capacity and coupling means, the network being resonant to a frequency at the high frequency end of the amplifier frequency range, said network comprising an inductance in series with the capacity and coupling means and a condenser in shunt with the coupling means.

8. In an amplifier, the combination with a tube provided with an anode circuit, a choke coil connected in the circuit, an anode potential source connected to the coil, a capacity, an inductive coupling means connected to said anode circuit through said capacity, a network connected between the capacity and coupling means, the network being resonant to a frequency at the high frequency end of the amplifier frequency range, and a condenser connected in shunt with the tube, between the anode and cathode thereof, to secure a sharp cut-off at said high frequency end.

POPKO REINDER DYKSTERHUIS. 

